Research On Key Techniques For Antifriction And Abrasion Resistance Of Micro-textured Self-lubricating Spherical Plain Bearing Surface Based On Aluminum Alloy

With swift development of aerospace,rail transit and other industries,the performance of specific substrate materials for self-lubricating spherical plain bearings has been required to be higher in practical engineering.High strength spherical plain bearing based on aluminum alloy are being paid more and more attention due to its high comprehensive mechanical properties,thermal conductivity and excellent corrosion resistance.However,aluminum alloy possesses some disadvantages,such as low hardness,large machining deformation and hard precision machining.In this paper,7075-T651 aluminum alloy was taken as substrate material for the research.The feasibility of aluminum-based self-lubricating spherical plain bearing was analyzed by finite element analysis.At the same time,In order to improve anti-friction and abrasion resistance properties of aluminum-based self-lubricating spherical plain bearings,multi-component of nano lubricants was optimized on the surface of which was treated by laser surface texturing and Ti-Al-Si-N hard coatings.Firstly,analytical calculation models of relative deformation and contact stress of aluminum-based self-lubricating journal bearings were established respectively,while the rated static load analysis of three kinds of self-lubricating journal bearing models based on ANSYS Workbench was carried out.Secondly,effect of texture parameters（single pulse energy,impulse repetition and repetition frequency）of nanosecond laser on surface morphology parameters of laser textured 7075 aluminum alloy was systematically investigated.Besides,pin-block reciprocating tests were carried out by MFT-5000 friction-and-wear tester to inspect the effects of different surface treatment methods,texture density,texture depth and working conditions on tribological properties of aluminum alloy friction pairs under grease lubrication.At the same time,four nano-lubricants were selected for single-factor friction test and four-factor three-level orthogonal optimization test.At last,Ti-Al-Si-N coating treatment was sputtered on the textured aluminum-based self-lubricating surface while the effects of different surface treatment methods,texture density and working condition parameters on tribological properties of the textured Ti-Al-Si-N coating/self-lubricating friction pair under the optimal quaternionic nano-composite lubrication condition were investigated.Remarkable conclusions of the above research work are as follows:（1）Distribution of equivalent contact stress and deformation of three groups of different substrate models are similar.Overall contact stress of the models concentrates on the upper surface of the contact area between the outer ring and the loading plate as well as the edge of inner ring end face,while the overall deformation concentrates on the edge of outer ring surface.Maximum equivalent stress of 7075 aluminum alloy model is 447.09MPa while maximum deformation is 0.0738mm.（2）With the increase of single pulse energy,the diameter and depth of aluminum micro-dimples both increase steadily.As pulse repetition increases,texture depth of aluminum micro dimple increases steadily（increment of each pulse number is about 5μm）,while the texture diameter increases briefly at first and then decreases slowly.With the increase of pulse repetition frequency,the diameter and depth of micro-pits decreases obviously.（3）Under grease lubrication condition,laser surface texturing can effectively decrease friction coefficient of aluminum-based self-lubricating friction pair and avoid failure caused by adhesion and brittle flaking on the surface of aluminum-based friction pair.The friction coefficient of aluminum-based textured self-lubricating specimen with 15%density and 12μm depth is the lowest.（4）Among the four nano lubricants,nano-WS₂ shows the optimal lubricating performance,which is in contrast of few-layer graphene.When the ratio of nano-graphite:Mo S₂:WS₂:few layer graphene is 1:1:3:0.5,the nano-composite lubricant can exert the optimal lubricating effect that is better than that of single lubricant.（5）Compared with single surface treatment,integration of laser surface texture and Ti-Al-Si-N coating can more effectively improve anti-friction and abrasion resistance properties of aluminum-based self-lubricating friction pair under the condition of non-lubrication and nano-composite lubrication.Textured coating surface with 25%density shows the optimal effect for anti-friction.